1. Field of the Invention
The present invention relates to a DC/DC converter (also called as a boosting circuit) and a semiconductor device using the DC/DC converter.
2. Description of the Related Art
In recent years, wireless chips which transmit and receive data wirelessly have been developed actively. The wireless chips which transmit and receive data are called an RFID (Radio Frequency Identification) tag, an RF tag, an RF chip, a wireless tag, a wireless processor, a wireless memory, an IC (Integrated Circuit) tag, an IC label, an electronic tag, an electronic chip, or the like. The wireless chips using a silicon substrate is the mainstream in the wireless chips which has already been put into practice.
The wireless chips which transmit and receive data wirelessly (hereinafter, referred to as RFID tags) generally have a structure in which inside circuits are made to operate by power obtained wirelessly. In the structure, each circuit is made to operate by using power from an antenna via a power supply circuit, a constant voltage circuit, or the like. That is, it can be considered that the power is supplied from only an antenna circuit.
Further, as the RFID tag becomes to have a higher function, it is required to mount a circuit needing high voltage for operation. For example, in the case where a floating gate type nonvolatile memory is mounted on the RFID tag, it is necessary to increase voltage to be high for power supplied from the power supply circuit or the constant voltage circuit. This is caused by the principle of the nonvolatile memory needing the high voltage when data is written. As long as such memory is used, it is difficult to avoid increase of the voltage. In order to satisfy the requirement of high voltage, a structure is considered, in which an RFID tag is provided with a DC/DC converter (see Reference 1: Japanese Published Patent Application No. 2006-109429).